1. Field of the Invention
The present invention relates to height-adjustable support arms, and in particular to such a support arm having a parallelogram linkage for supporting a hanging device, such as a dental lamp.
2. Description of the Prior Art
Height-adjustable support arms having a parallelogram linkage are known in the art for supporting various types of hanging objects and devices, such as a dental lamp. Such known support arms commonly have a first articulated head which is stationary and a second articulated head which is movable relative thereto for height adjustment. Such devices have a tubular member forming a first parallelogram leg disposed between the articulated heads and a rod forming the second parallelogram leg which is guided in the tubular member. Such devices further have a support bar mounted on the second articulated head at a free end of which the supported device, such as the dental lamp, is mounted.
Such conventional height-adjustable support arms have the disadvantage, particularly in employment in the medical and dental fields, that the movable parts which are visible from the exterior have gaps which permit the collection and penetration of dirt. The presence of the gaps additionally makes such surfaces difficult to clean to the standards necessary for medical use.